U.S. Pat. Nos. 3,857,677 and 3,725,003 disclose a method for the sterile packaging of articles sealed in containers. These patents rely only on heating the contents of the sealed container, including the anti-bacterial agent, to a temperature substantially below the boiling point in order to obtain complete sterilization of the inner surfaces of the container, which includes the surfaces in the air space. The reason that the surfaces in the air space become sterilized is that during the heating of the container and its contents the air inside the package becomes humidified with the aqueous solution that has an anti-bacterial agent in it. Therefore, the anti-bacterial agent becomes present in the air/gas and performs the sterilization process. If the sterilizing agents were not present in the air such low temperatures and pressures as disclosed in these patents would not produce a sterile condition.
There has been previous attempts to sterilize using a similar process with only water and saline being present in the liquid. This was disclosed in U.S. Pat. No. 3,754,368. This patent discloses that the time necessary for sterilization with water and/or saline is longer than if an anti-bacterial agent is present in the solution.
The problem with these processes as claimed and disclosed is that they do not allow a way to predict when sterility occurs other than actually testing the inside of the container and its contents usually with spore strips that must be incubated after being removed from the container. The result is that the heating process is performed for a time which is much longer than necessary to sterilize or a periodic sterility test must be performed during the heating procedure. The reason that it is difficult to predict when sterility occurs is that the humidity of the air, which is present when the container is sealed, can vary with each container depending on the atmospheric temperature and humidity present at the time the container is sealed. Therefore, the amount of anti-bacterial agent is variable because it is contained only in the aqueous solution and can only be placed in the air space by raising the humidity level in said space. As an example, using the same solution and anti-bacterial agent, if the atmospheric air which becomes sealed in the container is at 70.degree. F. and 40% relative humidity is heated to 120 .degree. F. during the heating process for four hours, the amount of additional humidity received from the aqueous solution in the container is different from a container which is sealed at a time when atmospheric air is 80.degree. F. and 80% relative humidity for the same heating cycle. Thus, the amount of anti-bacterial agent in the air space is different for each container.
Another problem which becomes apparent with the method of sterile packaging disclosed in U.S. Pat. No. 3,857,677 and 3,725,003 is that it allows the method of wetting articles as disclosed in U.S. Pat. No. 5,044,141 to be an inconsistent procedure. This is because the condensed solution which wets the surfaces above the liquid contains varying amounts of anti-bacterial agent which again depends on the atmospheric air temperature and humidity present at the time of sealing the container. This variation in the amount of anti-bacterial agent hinders the effectiveness of the wetting procedure disclosed.